The invention relates to dyeing agents having a special zwitterionic surfactant and which are suitable for being applied in the form of stable foam by special application devices, a dyeing process involving the use of the agent and the application device, as well as a corresponding kit for dyeing keratin-containing fibers.
Generally, either substantive dyes or oxidation dyes resulting from oxidative coupling of one or more developer components with each other or with one or more coupler components are used for dyeing fibers containing keratin. Coupler components and developer components are also called oxidation dye precursors. The developer components are normally primary aromatic amines with an additional free or substituted hydroxyl or amino group in the para or ortho position, diaminopyridine derivatives, heterocyclic hydrazones, 4-aminopyrazolone derivatives as well as 2,4,5,6-tetraminopyrimidine and derivatives thereof. m-Phenylenediamine derivatives, naphthols, resorcinol and resorcinol derivatives, pyrazolones, m-amino phenols and substituted pyridine derivatives are generally used as the coupling components.
In order to stabilize the dye precursors during storage and for accelerating the reaction during the oxidative application, oxidation dyes mostly exhibit an alkaline pH value that is adjusted with alkalizing agents, such as alkanolamines, ammonia or inorganic bases. Although ammonia in particular enables good dyeing results, it also manifests disadvantages for the user due to its odor and irritation potential for skin and mucous membranes. Consequently, increased efforts have been made to develop efficient oxidative dyes that dispense without the use of ammonia.
Oxidative dyes usually consist of a mixture of two components, with the mixture being sufficiently viscous to allow it to be comfortably applied onto hair without any dripping or running. There have also been frequent attempts to develop other presentation forms. Thus, it has been proposed to deposit lower viscosity dyes onto the hair with special applicator systems or to apply dyes as foam. In particular, the use of aerosol foams is widespread for foam application. Recently however, there has been a requirement to eliminate the use of propellant gases.
Another problem associated with foam application is stabilization of the foam. The consistency of foams is considered to be ideal when the dispensed product affords solid, stable foam that leaves a supple feel and breaks down only slowly on the hair. It is frequently observed, however, that the applied foams possess little stability and rapidly collapse, leaving behind a low viscosity solution that drips. Still, it is also important that the foam wets the hair well so that a good color application can be realized. Foam stability is negatively influenced in particular by the presence of larger amounts of salts and dye (precursor)(s). Hair treatment agents in the form of foams are already known from JP 10-167938 A. Betaine surfactants of the alkyl dimethyl betaine type and the (fatty acid amidoalkyl) dialkyl betaine type, such as cocoamidopropyl betaine, are disclosed as particularly suitable surfactants for a stable foam formation of acidic, hydrogen peroxide-containing hair treatment agents. Cocoamidopropyl betaine is also described in WO 2006/066642(A1) as a suitable surfactant with high surfactant content in tinting foams based on substantive dyes.
However, it has been shown in extensive tests that the strongly alkaline oxidation dye preparations pose particular challenges to the foam-forming surfactant. In particular, foaming oxidation dye preparations with high amounts of fatty acid amidoalkyl betaines as the foam-forming surfactant tend to develop amine-like odors, particularly in the presence of alkanolamines as the alkalizing agent, which are perceived by the user as disturbing and unpleasant.